Are Nasus stacks critting? Explain these numbers...

This may go unnoticed on most normal Nasus builds, but I've noticed some funny things whenever I experiment with crit on him (it's S6, don't even pretend you're shocked.) A while back, I got a 2400 crit strike in postgame stats on Nasus. I couldn't figure out how the math worked out, unless my Q stacks were critting as well (or sheen, which would be new.)

I don't have the build for that game, but take this one for instance:

http://i.imgur.com/Wpqhppq.png

This was my end-game build, and I had about 100 stacks (it's ARAM, don't judge me)

But my largest crit strike was 1643. Last time I looked at my ad, it was 300ish. So that's a 750, or round up, 800 crit strike on AD. Add sheen, that's 1000, and... wat... where the heck does the other 650 come in? I had 100 stacks... what is this...